Explanation:
Why is there a blue bridge of stars across the center of this galaxy cluster?
First and foremost the cluster, designated
SDSS J1531+3414,
contains many large yellow
elliptical galaxies.
The cluster's center, as
pictured above
by the Hubble Space Telescope, is surrounded by many unusual, thin,
and curving blue filaments that are actually galaxies far
in the distance whose images have become magnified and
elongated by the gravitational lens
effect of the massive cluster.
More unusual, however, is a
squiggly blue filament
near the two large
elliptical galaxies
at the cluster center.
Close inspection
of the filament indicates that it is most likely a bridge created by tidal effects
between the two merging central elliptical
galaxies
rather than a background galaxy with an image distorted by
gravitational lensing.
The knots in the bridge are
condensation regions that glow blue from the light of massive young stars.
The central cluster region will likely undergo continued study as its uniqueness makes it an interesting laboratory of
star formation.